A requirement for scraper devices for conveyor belts arises in many fields of activity, particularly those of minerals processing and mining where irregularly shaped items of varying size, compacted with liquids such as to adhere to the belt have to be conveyed in a very aggressive environment. The conveyor belt scraper of the present invention generally comprises one or a plurality of lever arms pivotally mounted for turning movement about one end and carrying one or a plurality of scraper blades at the other, which arm or arms is or are resiliently biased to turn about the said pivot axis in order to bring the scraper blade into contact with a moving member such as a conveyor belt which is to be scraped. Such a scraper is particularly useful for scraping the return run of a conveyor belt used to convey crushed rock or minerals or other mining products such as coal all of which tend to form accumulations of small particles and moist dust coagulating on the surface of the conveyor belt which, in the absence of the scraper device of the present invention, would tend to accumulate on the belt itself.
Conveyor belt scrapers as such are known. One such scraper is described in UK Patent 1,553,210. This known scraper comprises two pivoted arms between which a scraper blade is carried, each arm being pivotally mounted to turn about a common pivot axis by respective torsion rubber bushes which are vulcanised or otherwise bonded between two rigid sleeves one fixedly connected to the arm to be pivoted and the other fixedly connected to a support structure. The known torsion rubber bush pivot and biasing constructions have the advantage over other known structures of being particularly compact and relatively easy to adjust, so that they can be used in locations where less compact structures cannot be fitted. They do have a major disadvantage, however, due to the fact that they are in use subjected to a dynamic stress pattern from fluctuations in the position of the conveyor belt as it moves, which tends to fatigue the bond between the rubber and the sleeves resulting, on occasion, in failure of this bond and consequent loss of torsion to the scraper blade support arms. Such failure is catastrophic in the sense that all biasing tension is completely lost once the bond is broken so that the scraper fails entirely in service.
Another disadvantage of the known torsion rubber bush biased scrapers lies in the relatively high expense involved in producing the torsion bushes which require special press equipment for assembly and vulcanisation. Although positional adjustment is relatively easy with the known devices it is not readily possible to vary the range of forces to which such devices may react, for example for the purpose of adapting the scraper for use on different belts of larger width which, because of this, would exert a higher force. Considerable modification to the length and/or diameter of the torsion bushes is required in order to accommodate such force variation and these, therefore, must be made for intended use within rather limited ranges.